/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.search;

import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import java.util.Map;

import org.apache.solr.common.SolrException;
import org.apache.solr.util.DOMUtil;
import org.apache.solr.core.SolrConfig;
import org.apache.solr.core.SolrResourceLoader;

import javax.xml.xpath.XPathConstants;

/**
 * Contains the knowledge of how cache config is stored in the solrconfig.xml
 * file, and implements a factory to create caches.
 * 
 * 
 */
public class CacheConfig {
	private String nodeName;

	private Class<? extends SolrCache> clazz;
	private Map<String, String> args;
	private CacheRegenerator regenerator;

	private String cacheImpl;

	private Object[] persistence = new Object[1];

	private String regenImpl;

	public CacheConfig() {
	}

	public CacheConfig(Class<? extends SolrCache> clazz,
			Map<String, String> args, CacheRegenerator regenerator) {
		this.clazz = clazz;
		this.args = args;
		this.regenerator = regenerator;
	}

	public CacheRegenerator getRegenerator() {
		return regenerator;
	}

	public void setRegenerator(CacheRegenerator regenerator) {
		this.regenerator = regenerator;
	}

	public static CacheConfig[] getMultipleConfigs(SolrConfig solrConfig,
			String configPath) {
		NodeList nodes = (NodeList) solrConfig.evaluate(configPath,
				XPathConstants.NODESET);
		if (nodes == null || nodes.getLength() == 0)
			return null;
		CacheConfig[] configs = new CacheConfig[nodes.getLength()];
		for (int i = 0; i < nodes.getLength(); i++) {
			configs[i] = getConfig(solrConfig, nodes.item(i));
		}
		return configs;
	}

	public static CacheConfig getConfig(SolrConfig solrConfig, String xpath) {
		Node node = solrConfig.getNode(xpath, false);
		return getConfig(solrConfig, node);
	}

	public static CacheConfig getConfig(SolrConfig solrConfig, Node node) {
		if (node == null)
			return null;
		CacheConfig config = new CacheConfig();
		config.nodeName = node.getNodeName();
		config.args = DOMUtil.toMap(node.getAttributes());
		String nameAttr = config.args.get("name"); // OPTIONAL
		if (nameAttr == null) {
			config.args.put("name", config.nodeName);
		}

		SolrResourceLoader loader = solrConfig.getResourceLoader();
		config.cacheImpl = config.args.get("class");
		config.regenImpl = config.args.get("regenerator");
		config.clazz = loader.findClass(config.cacheImpl, SolrCache.class);
		if (config.regenImpl != null) {
			config.regenerator = loader.newInstance(config.regenImpl,
					CacheRegenerator.class);
		}

		return config;
	}

	public SolrCache newInstance() {
		try {
			SolrCache cache = clazz.newInstance();
			persistence[0] = cache.init(args, persistence[0], regenerator);
			return cache;
		} catch (Exception e) {
			SolrException.log(SolrCache.log, "Error instantiating cache", e);
			// we can carry on without a cache... but should we?
			// in some cases (like an OOM) we probably should try to continue.
			return null;
		}
	}

}
